Why the scripts taken into account for calculating sensex are 30 only? why not 40 or 50?

Question

Why the scripts taken into account for calculating sensex are 30 only? why not 40 or 50?

Answer 1

it is like saying why humans have 2 legs and not 4.

however, the basic principal behind it is that according to BSE exchange, these 30 stocks together comprise majority of trade (out of total trade for a day), therefore, an index of these 30 would give a comparative idea of the market trends. any additional increase in this list of 30 would not change the overall pattern of stock market trend and therefore, not required to be added to the list.

however, nse differs frm this and nifty has 50 stocks. they believe 50 shares are required to tap market trends on trades in NSE exchange.

in any case, the total volume of trade on nse is way higher than bse, therefore, nse may be right in taking a broader list to map the trend.